#define fetPin 2
#define potPin A0
#define ledPin 13
 
#define highms 500
#define lowms 20
 
float pot = 0;
float total = 0;
float ondelay = 0;
float offdelay = 0;
 
void setup()
{
  Serial.begin(9600);
  pinMode(fetPin, OUTPUT);
  pinMode(ledPin, OUTPUT);
  pinMode(potPin, INPUT);
  total = highms-lowms;
}
 
void loop()
{
  pot = analogRead(potPin);
  pot /= 50.0;
  pot = 1 - pot;
  if(pot > 1) pot = 1;
  if(pot < 0.04) pot = 0.04;
  
  offdelay = total*pot*pot;
  ondelay = total*pot-offdelay;
  
  Serial.print(pot);
  Serial.print("   ");
  Serial.print(ondelay);
  Serial.print("   ");
  Serial.println(offdelay);
  digitalWrite(ledPin, 1);
  digitalWrite(fetPin, 1);
  delay(ondelay);
  digitalWrite(ledPin, 0);
  digitalWrite(fetPin, 0);
  delay(offdelay);
}